The present invention relates to an apparatus for producing soft serve dairy products, in particular yogurt. High quality yogurt is especially difficult to produce because of high demands to its smoothness, creaminess, and consistency.
Apparatus for producing soft serve dairy products are known. The main parts of such apparatus are a hollow freeze cylinder or a barrel and a motor driven so-called beater shaft assembly located inside of the cylinder for advancing a product mix from an inlet port to an outlet port while whipping and mixing the product mix. The beater shaft assembly includes a rotatable shaft and a plurality of blade elements mounted on the shaft for propelling the product forward and for scraping the product from the barrel wall and placing the product in the path of the propelling blades. An apparatus of this type is disclosed in U.S. Pat. No. 2,491,852 of the applicant herein. The apparatus of U.S. Pat. No. 2,491,852 comprises a hollow cylinder and a beater shaft assembly mounted inside the cylinder. The shaft assembly includes a circular shaft and a plurality of combined propeller and scraper elements mounted thereon. Each blade element includes a collar slidably mounted on shaft, a curved propeller blade extending radially outwardly from the collar, an arm also extending radially outwardly from the collar but from a side thereof which is opposite to the side from which the propeller blade extends, and a scraper member having a pair of legs for straddling the arm, a shaft extending across the leg and fittable into a semi-circular recess formed at the arm top, and a scraper component supported by the legs. As can be seen from the foregoing description, the beater shaft assembly of U.S. Pat. No. 2,491,852 is rather complex. Beside, what is more important, the apparatus of U.S. Pat. No. 2,491,852 does not permit the production of yogurt with good smoothness and consistency.
A simplified beater shaft assembly is disclosed in Canadian Patent No. 494,346 of the applicant herein. The beater shaft assembly disclosed therein includes a square shaft from the four faces of which extends radially therealong a plurality of pins arranged in pairs, and a plurality of spirally shaped blade elements mounted on respective pairs of pins. As in U.S. Pat. No. 2,491,852, the blade elements perform the propelling and the scraping functions. Each blade element has a substantially rectangular base the side edges of which substantially coincide with respective edges of the shaft. The base has a pair of spaced openings for engaging a respective pair of pins. A spiral fin or vane projects from the base body. The opposite end portions of the spiral fin or vane project beyond the side edges of the base. The blade elements are arranged progressively offset relative to each other on successive faces of the shaft in such a manner that end of one blade element extends a substantial distance beyond ends of adjacent blade elements and that the vanes form a substantially spiral formation due to the end portions of the vanes extending beyond the side edges of the base. The pairs of pins are arranged on the shaft in an overlapping manner; that is, the last pin of a preceding pair extends beyond the position of the first pin of the successive pair of pins in a direction of product mix movement. While an apparatus for producing soft serve dairy products having a beater shaft assembly of the Canadian patent has improved operational characteristics, still it was unable to produce a frozen yogurt with sufficient smoothness, creaminess and homogeneity.
The object of the invention is to provide an apparatus for producing soft serve dairy products and especially yogurt having a very good smoothness, creaminess and thorough homogeneity. Another object is to use such apparatus in a continuous serve machine.